1. Field of the Invention
This invention relates to lift chairs for use by elderly, disabled and infirm persons. The lift chair reclines from a normal, upright, seated position to a position in which the chair back has reclined and a leg support platform has moved from vertical to horizontal to provide support for the reclining occupant's leg. The lift chair can be returned from the reclining position to an upright position whereupon the lift chair can be actuated through a continuous range of motion to lift and pitch forward thereby assisting the chair occupant in arising from the chair.
2. Description of the Prior Art
U.S. Pat. No. 3,138,402 discloses an invalid chair having a pivotally mounted seat or cushion portion, divided into front and rear cushioned sections. A four bar linkage is utilized to lift the rear cushioned section separating the same from the front cushioned section and is actuated by a bell crank shaped link 63. Two links 19, 22 and plate portions between pivots 21 and 23 at the front and pivots 36 and 37 at the rear form a parallelogram or four-bar linkage support. This support produces rotation of a front cushioned section 31 and upward and forward movement of chair frame 24 from the position illustrated in FIG. 1 of '402 to the position illustrated in FIG. 2 of '402 (Column 3, lines 41-48 and FIGS. 1 and 2 of U.S. Pat. No. 3,138,402). A motor drives a lead screw in a direction to move a nut 41 to the rear in '402. This moves operating links 58 and bell crank link 63 to the rear, causing projecting end 66 thereof to engage a cross-brace 29. This, in turn, moves links 19 and 20 counterclockwise, rotates the front cushioned section 31 about a pivot 21 and raises chair frame 24 upwardly and forwardly to the position illustrated in FIG. 2 of '402. This raises and slides the occupant forwardly from the rear cushioned section into a standing position (Column 4, lines 20-27 of '402).
'402 also discloses an ottoman or leg support structure as an option in FIG. 4 thereof. By moving a switch actuating element 69 of a switch 67 to position for raising chair frame 24, the motor of '402 is reversed to drive a nut to the rear, permitting springs 91 to return the ottoman of '402 to its nested position, as illustrated in FIGS. 1 and 2 of '402. The switch is released at this point unless the occupant desires to be raised to standing position in which case holding the switch in the position for retracting the ottoman continues to drive nut 41 to the rear on lead screw 39, thereby moving the chair frame to a raised position as illustrated in FIG. 2 of '402 (Column 5, lines 3-13 of '402).
U.S. Pat. No. 4,007,960 discloses a reclining elevator chair which, in a first mode of operation, has drive means which drives a reclining mechanism to tilt the back of the chair and extend and retract the leg rest. In the second mode of operation, the drive means drives the elevator mechanism to raise the seat of the chair and tilt it slightly forward. Near the upper end of the elevation range of the chair seat, the mechanism is effectuated to tilt the seat back rearwardly to avoid imposition of objectionable pressure on the occupant of the chair (Column 1, lines 20-28 of '960). Transfer between the first and second modes of operation is effectuated by a ram acting through a part of its range of extension to swing a crank about its pivot to drive a recliner mechanism in the first mode. When the ram acts through a different part of its range, it abuts the crank against the seat frame to inactivate the recliner mechanism and drives the elevator mechanism in the second mode (Column 1, lines 31-37 of '960).
In the first mode of operation, the power actuated drive means drives the recliner actuator means or mechanism to tilt the chair back 12 to a recline position illustrated in FIG. 3 of '960 and to simultaneously extend and tilt a leg rest 16. In a second mode of operation, the same drive means drives elevator means or mechanism to raise seat 14 and tilt it forwardly as illustrated in FIGS. 4 and 11. Sides 10, back 12 and leg rest 16 rise along with seat 14 in the second mode of operation (Column 2, lines 27-30 and 32-37 of '960).
The elevator means or mechanism includes two sets of paired laterally spaced arms 26 and 28 pivotally connected at the rear ends by pintles 30, 32 to corresponding plates 24 at opposite sides of the chair. The forward ends of swing arms 26 and 28 are pivotally connected to corresponding laterally spaced seat support plates 34 illustrated in FIGS. 7 and 9 of '960 (Column 2, lines 54-60 of '960).
U.S. Pat. No. 4,852,939 discloses a device for converting a recliner chair to a recliner-lift chair.
Use of paired laterally spaced arms 26 and 28 as disclosed in '960 has been implemented in a manner to drive a lift chair seat portion using a bracket and pivot arrangement as illustrated in FIG. 26 where a prior art linkage mechanism is illustrated isometrically and partially broken and is designated generally 500. A drive extension shaft from a motor is designated 502 and is connected via a collar 504 and a pin 506 to a pair of plates 508 defining a bracket designated generally 510 which is fixedly connected to a cross-bar 512 of a T-member designated generally 514. A leg portion 516 of T-member 514 is pivotally retained in a bracket 518 defined by two parallel plates 520 with the point of pivotal connection between leg 516 and bracket 518 being defined by pivot rod 522. Bracket 518 is secured to a cross-member 524 of a lift chair frame by welding; cross-member 524 is elevated together with the lift chair upon drive extension shaft 502.
Pivotally connected to cross-bar 512 are a pair of chair seat portion support arms 526 which are pivotally connected to extension tabs 528 formed at the ends of and integrally with cross-bar 512. with pivotal connection between extension tabs 528 and seat portion support arms 526 effectuated via pins 530.